October 2: PhD defence Shahrokhvand on Magneto-Resistance and Thermoelectric Power of Conventional and Topological Materials
A topological future?
The discovery of topological materials (e.g. topological insulators or Weyl semimetals) has opened up the possibility of a new revolution in electronic devices. The topological protection inherent in these materials gives rise to interesting electronic properties such as current flow with minimal dissipation.
Two is better than one
Maryam Shahrokhvand dedicated her PhD to understanding of these new materials by measuring their electronic and thermal properties. She employed two complementary techniques during her PhD; magneto-transport and thermoelectric power. She performed these experiments under the extreme conditions of low temperatures and high magnetic fields. Under these conditions, the electronic energy levels of the material become quantized into so-called Landau levels. This quantization leads to an oscillatory pattern in physical properties like electrical resistance and thermopower as a function of the magnetic field strength. From the analysis of these oscillations, Maryam extracted useful information about material-specific properties. These investigations also helped her to disentangle those electronic properties due to topological protected states from those with a trivial (non-topological) origin. In addition, Maryam was able to identify the origin of one particular phase transition that would not have been possible without the combination of techniques that she employed.
Physical and personal horizons broadened
“What makes condensed matter physics interesting for me is the fact that macroscopic properties, like electrical resistance, can be explained by the microscopic arrangement of electrons in their individual energy levels. Performing the experiments themselves was fascinating and analyzing the data was one of the most interesting parts as I could find the answer to a specific outstanding problem. Apart from that, doing a PhD in a European user facility was a very interesting experience as we helped guests from around the world to perform their experiments at HFML. I got the chance to meet scientists from many different universities in Europe. These opportunities certainly helped to broaden my horizons.”
Maryam Shahrokhvand defended her doctoral thesis on Wednesday October 2.
Supervisor: prof. dr. N.E. Hussey, Prof.dr. U. Zeitler
Co-supervisors: dr. S.R. Wiedmann